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A method to avoid debonding forces on flexible semiconductor films disposed on different adhesives

IP.com Disclosure Number: IPCOM000239424D
Publication Date: 2014-Nov-05
Document File: 5 page(s) / 137K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that makes it possible to bond a flexible semiconductor layer to a (rigid) low cost substrate coated with an epoxy adhesive or any kind of adhesive in such a manner as to allow it to fabricate devices and avoid any problem related to debonding forces due to adhesive outgassing.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 44% of the total text.

Page 01 of 5

A method to avoid debonding forces on flexible semiconductor films disposed on different adhesives

A new technology, called spalling, is used to reduce the total cost of optoelectronic devices such as solar cells. In this technology, a stressor layer is used to exfoliate a thin, device quality, semiconductor layer from a parent semiconductor substrate . This process can be repeated multiple times, limited only by the thickness of substrate. The thin, typically flexible, semiconductor layers can be difficult to handle and process .

In many cases, it is desirable to have a method that allows the flexible semiconductor layer to bond (at least temporarily) to a (preferably rigid) low cost handle substrate. The bonding method needs to be compatible with semiconductor layer /handle substrate processing at temperatures as high as 200 400C. The bonding temperature is limited by the maximum temperature that can be handled by the tape (i.e. ultra violet (UV) releasable tape or polyimide tape (maximum temperature 90oC and 200oC, respectively)) contacting the stressor layer used for spalling. Epoxy bonding is one preferred bonding method. However, post bonding processes, at temperatures higher than the curing temperature of the epoxy, leads to both blister formation and adhesion failure between the impermeable flexible film and the epoxy , an effect attributed to epoxy outgassing.

It is therefore desirable to find a method that solves this problem of providing a bond between the flexible semiconductor layer and a low cost handle substrate, without the negative side effects of epoxy outgassing. At present, no such method exists.

The problem with the prior art process is shown schematically in Figure 1.

Figure 1: An unsatisfactory method of bonding a flexible semiconductor to a rigid substrate using epoxy (flexible semiconductor film disintegrates upon post bonding process at temperature higher that the curing temperature of the epoxy )

1


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Disclosed is a method that makes it possible to bond a flexible semiconductor layer to a (rigid) low cost substrate coated with an epoxy adhesive or any kind of adhesive in such a manner as to allow it to fabricate devices and avoid any problem related to debonding forces due to adhesive outgassing. The method consists of forming the metal pattern on the original wafer to be spalled, and then perform the sintering or annealing of the metal. This step is followed by the spalling of the film comprising the metal pattern and bonding it to any kind of low cost rigid substrate. Using this process, the post bonding process that is responsible of adhesive outgassing, and consequently semiconductor film debonding, is eliminated. This method provides more flexibility in terms of the bonding process. For example, the method allows the use of wax as a low cost adhesive that does not require a curing process, as well as the use of different metal contacts. Prior to this method, the use of low temperature met...